The field of this invention relates to automatic welding equipment and more particularly to a welding apparatus which locates the filler wire assembly in a precise position in respect to the welding electrode regardless of the direction of movement of the welding electrode along the weld path and accurately maintains constant the physical spacing of the electrode from the weld path.
It is well known to employ the use of welding electrode assemblies within apparatuses for automatic welding structures. The welding electrode is to move along the weld path during the welding of the structure. The filler wire, which is melted by the electrode and ultimately forms the weld bead, is to be located just forward of the welding electrode. The welding electrode is to be movable in a given direction, either lineally or arcuate. Just forward is to be defined as along the direction of movement and just ahead of the tip of the welding electrode.
Generally, automatic welding apparatuses are employed to weld regular shaped structures, such as cylinders, spheres and the like. In the welding of such regular shaped structures, the welding electrode begins movement at a particular point and moves along the weld path to return to this particular point without ever changing directions of movement. In such an instance, it is only required that the filler wire assembly be initially positioned with respect to the welding electrode and it will remain in that position along the entire weld path.
However, a problem arises if the weld path is not regular. For instance, in the event that the weld path is polygonal shaped, or the weld path does lie within a single plane and the welding electrode must move within three dimensions in order to move along the weld path. This means that the welding electrode will move to the right or to the left. However, the filler wire assembly must be turned in respect to the workpiece in order to locate the filler wire assembly in its required position. Examples of such irregularly shaped weld paths may be on odd shaped parts, such as engine cowlings for aircraft.
Automatic welding apparatuses are not designed to weld only an individual part. Usually there are a plurality of parts which are to be welded in the same location. Each of the structures are to be an exact replica of each other. However, there are inherently produced small discrepancies between one part and another part. These small discrepancies will affect the preprogrammed weld path resulting in the welding electrode being spaced either too close or too far away from the weld path. A minute change in this spacing can seriously affect the quality of the weld. Previously, it is believed that there has not been an automatic welding apparatus which precisely controlled the position of a welding electrode along a preprogrammed weld path.